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Since the advent of the industrial revolution, the use of non-water-based chemicals has increased dramatically. Exposure to the hazards associated with these chemicals has also increased.
One potential hazard is flammability. To prevent fires, hazardous liquids need special precautions taken for their storage, handling and use. The National Fire Protection Agency (NFPA) and the International Code Council (ICC) have developed guidelines for the safe storage and use of flammable and combustible liquids under the Uniform Fire Code. These guidelines are not mandatory unless a federal, state or local authority chooses to use them.
Mandatory regulations have been developed, however, by Occupational Safety and Health Administration (OSHA). They have specified safe handling practices under three separate mandatory regulations for:
- General Industry (29 CFR 1910.106)
- Construction Industry (29 CFR 1926.152)
- Shipyard Industry (29 CFR 1915.36)
For the purpose of this document, only the requirements of the General Industry will be discussed.
Defining Flammable and Combustible LiquidsTo understand OSHA requirements for the safe storage of flammable and combustible liquids, we must begin by defining the two. The flashpoint and boiling point determine the class of a liquid.
A flammable liquid is any liquid having a flashpoint below 100° F (37.8°C) (except any mixture having components with flashpoints of 100°F (37.8°C) or higher, the total of which make up 99 percent or more of the mixture)(1910.106(a)(19)). Flammable liquids are categorized into three groups, as follows:
- Class IA Flammable Liquid
Liquids having flashpoints below 73°F (22.8°C) and having boiling points below 100°F (37.8°C) (1910.106(a)(19)(i)). Examples: Acetaldehyde, ethyl ether and cyclohexane. - Class IB Flammable Liquid
Liquids having flashpoints below 73°F (22.8°C) and having boiling points at or above 100° F (37.8°C) (1910.106(a)(19)(ii)). Examples: Acetone, benzene and toluene. - Class IC Flammable Liquid
Liquids having flashpoints at or above 73°F (22.8°C) and below 100° F (37.8°C) (1910.106(a)(19)(iii)). Examples: Hydrazine, styrene and turpentine.
A combustible liquid is any liquid having a flashpoint at or above 100°F (37.8°C) (1910.106(a)(18)). Combustible liquids are divided into two classes:
- Class II Combustible Liquid
Liquids having flashpoints at or above 100°F (37.8°C) and below 140°F (60°C), except any mixture having components with flashpoints of 200°F (93.3°C) or higher, the volume of which make up 99 percent or more of the total volume of the mixture (1910.106(a)(18)(i)). Examples: Acetic acid, naphtha and stoddard solvent. - Class III Combustible Liquid
Liquids having flashpoints at or above 140°F (60°C) (1910.106(a)(18)(ii)). Class III liquids are subdivided into two subclasses: - Class IIIA Combustible Liquid
Liquids having flashpoints at or above 140°F (60°C) and below 200°F, except any mixture having components with flashpoints of 200°F (93.3°C) or higher, the total volume of which make up 99 percent or more of the total volume of the mixture (1910.106(a)(18)(ii)(a)). Examples: Cyclohexanol, formic acid and nitrobenzene. - Class IIIB Combustible Liquid
Liquids having flashpoints at or above 200°F (93.3°C) (1910.106(a)(18)(ii)(b)). Examples: Formalin and picric acid. Per 1910.106(a)(18)(ii)(b) "Class IIIB liquids" shall include those with flashpoints at or above 200°F (93.3°C). This section does not cover Class IIIB liquids. Where the term "Class III liquids" is used in the section, it shall mean only Class IIIA liquids. (Class IIIB is used in this document for reference purposes only.)
*Note: When a combustible liquid is heated for use to within 30°F (16.7°C) of its flashpoint, it shall be handled in accordance with the requirements for the next lower class of liquids (1910.106(a)(18)(iii)).
Whether a liquid is a Class IB Flammable Liquid or Class IIIA Combustible Liquid is not the only factor you should consider when determining your safe storage needs. You also need to consider ignition temperature, explosive limits (LEL or UEL), vapor pressure, specific gravity and vapor density if you want to design a truly safe storage system.
Flammable and Combustible Liquids Safety CansOne technique to reduce the hazards associated with flammable and combustible liquids is the use of safety cans. OSHA defines a safety can as:
"An approved container, of not more than 5 gallons capacity, having a spring-closing lid and spout cover and so designed that it will safely relieve internal pressure when subjected to fire exposure" (1910.106(a)(29))."
This definition allows a wide variety of containers to be considered safety cans. However, many local laws and insurance carriers require safety cans to be Factory Mutual (FM) or Underwriter Laboratory (UL) approved. These two organizations are nationally recognized independent testing laboratories to which manufacturers submit products for evaluation of their ability to meet safety requirements under intended use. Products that meet the requirements are given either a UL product or FM approved. Both laboratories are also recognized by OSHA. (See our "Understanding ANSI, ASTM International, FM Global, NFPA, SEI and UL" EZFacts® Document No. 100 for more on these organizations.)
In addition, 29 CFR 1910.106 limits the amount of liquid in a single safety can. The following chart shows the allowable amounts for each class of liquid.
| Container Type | Flammable Liquids | Combustible Liquids | |||
|---|---|---|---|---|---|
| Class IA | Class IB | Class IC | Class II | Class III | |
| Glass or approved plastic | 1 pint | 1 quart | 1 gallon | 1 gallon | 1 gallon |
| Metal (other than DOT drums) | 1 gallon | 5 gallon | 5 gallon | 5 gallon | 5 gallon |
| Safety Cans | 2 gallon | 5 gallon | 5 gallon | 5 gallon | 5 gallon |
| Metal Drum (DOT spec.) | 60 gallon | 60 gallon | 60 gallon | 60 gallon | 60 gallon |
| Approved Metal Portable Tanks | 660 gallon | 660 gallon | 660 gallon | 660 gallon | 660 gallon |
There are exceptions to this rule:
- Medicines, beverages, foodstuffs, cosmetics and other common consumer products, when packaged according to commonly accepted practice
29 CFR 1910.106 also limits the total amount of a liquid kept outside of a safety cabinet or storage room. The quantity of liquid that may be stored outside of an inside storage room or flammable liquid storage cabinets in any one fire area of a building cannot exceed:
- 25 gallons of Class IA liquids in containers
- 120 gallons of Class IB, IC, II or III liquids in containers
- 660 gallons of Class IB, IC, II or III liquids in a single portable tank
The amount of liquid storage and location of cabinets is regulated. 1910.106 (d)(3) states, "Not more than 60 gallons of Class I or Class II liquids, nor more than 120 gallons of Class III liquids may be stored in a storage cabinet." Also, according to NFPA 304.3.2, not more than three (3) such cabinets may be located in a single fire area.
Storage CabinetsAnother fundamental means of fire protection is the use of flammable storage cabinets. The NFPA, OSHA and UFC require flammable cabinets to be designed and constructed to specific requirements. 1910.106(d)(3)(ii)(a) states that metal cabinet shall be constructed in the following manner:
- Bottom, top and sides of cabinet shall be at least No. 18 ga. sheet steel
- Cabinet must be doubled walled with 1½" airspace
- Joints shall be riveted, welded or made tight by some equally effective means
- Door shall have a three-point latch
- Door sill shall be raised at least 2" above the cabinet bottom to retain spilled liquid within the cabinet
- Cabinet shall have a "FLAMMABLE—KEEP FIRE AWAY" legend
These regulations also provide an option for wood cabinets. 1910.106(d)(3)(ii)(b) states that wood cabinets shall be constructed in the following manner:
- Bottom, top and sides of cabinet shall be at constructed of exterior grade plywood at least 1" thick
- Plywood shall not break down or delaminate under fire conditions
- Joints shall be rebutted and fastened in two directions with flathead wood screws
- When more than one door is used, they should have a rebutted overlap of not less than 1"
- Doors shall be equipped with latches and hinges that are mounted to not lose their holding capacity when subjected to fire
- Door sill or pan shall be raised at least 2" above the cabinet bottom to retain spilled liquid within the cabinet
- Cabinet must have a "FLAMMABLE—KEEP FIRE AWAY" legend
In addition to the requirements listed above, the UFC (Uniform Fire Code) also requires self-closing doors. Most local authorities use one or more of these standards as a foundation for establishing local codes.
Fire AreasOSHA does not provide a definition of a fire area in their standard. However, a fire area is defined by NFPA Code 30 (1.6.15) as, "An area of a building separated from the remainder of the building by construction having a fire resistance of at least 1 hour and having all communicating openings properly protected by an assembly having a fire resistance rating of at least 1 hour."
The NFPA also provides a special provision for the grouping of flammable cabinets in an industrial facility. Because most industrial settings do not have walls or barriers within a facility, "In an industrial occupancy, additional cabinets may be located in the same fire area if the additional cabinets, or the group of not more than three (3) cabinets, is separated from the other cabinets or group of cabinets by at least 100 feet (30 m)." (4.3.2 Exception 1)
Flammable Combustible Liquids QuestionsFrequently Asked Questions
Q. When dispensing flammable liquids, do I have to use bonding and grounding wires?
A. According to 1910.106(e)(6)(ii), only Class I liquids are required to be bonded and grounded. However, for your own safety, bonding and grounding should always be used when dispensing flammable or combustible liquids. See EZFacts® 255 for more information.
Q. Am I required to have a flammable storage cabinet?
A. OSHA does not require the use of flammable storage cabinets unless the total amount of flammable and/or combustible liquids reaches a given amount. Local authorities and insurance companies may require the use of flammable storage cabinets in quantities less than that of OSHA.
Q. What is the difference between type I and type II safety cans?
A. A Type I safety can has one spout for both pouring and filling. A Type II safety can has two openings; one for pouring and one for filling. See LSS Tech Clip 1 for more information.
Q. What is a flame arrestor, and what purpose does it serve?
A. A flame arrestor is a mesh or perforated metal insert within a flammable storage container (safety can, cabinet) which protects its contents from external flames or ignition. It also dissipates heat. All Type I, Type II, disposal and specialty cans include a flame arrestor.
Q. Are flammable cabinets required to have mechanical ventilation?
A. OSHA does not normally require the use of mechanical ventilation. The NFPA recommends that cabinets not be mechanically ventilated, but if they are, they should be ventilated in accordance to NFPA 91 Exhaust Systems for Air Conveying of Materials. See EZFacts® 215 for more information.
Flammable and Combustible Liquid ResourcesSources for More Information:
National Institute of Occupational Safety & Health, Pocket Guide to Chemical Hazards, U.S. Department of Health and Human Services. (Washington: GPO 2005).
National Fire Protection Association, Flammable and Combustible Liquids Code Handbook, Sixth edition, ed. Robert Benedetti, 1996.
United States Office of the Federal Register National Archives and Records Administration, 29 Code of Federal Regulations Parts 1900 to 1910, (Washington: GPO 1994).
National Fire Protection Association
